MASANGA HAEMOZOIN BIOSENSOR TRIAL
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Transcript of MASANGA HAEMOZOIN BIOSENSOR TRIAL
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MASANGA HAEMOZOIN BIOSENSOR TRIALCIARÁN DOHERTY
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Masanga HospitalA rural compound, providing free healthcare in paediatrics, maternity, general medicine and surgery in Tonkolili district, Sierra Leone.
Staffed largely by local auxilliaries, Dutch doctors and British & Danish volunteers.
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Sierra LeoneLocation: West Africa
Population: 6 million
Infamous for the brutal civil war between ‘91 & ‘02, the country is now at peace, although still remains one of the poorest in the world
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Malaria in Sierra Leone• Malaria is the 5th largest cause of death by infectious disease
worldwide, accounting for around 200 million cases per year and up to 1 million deaths
• 100% of Sierra Leone is classed as a high transmission zone
• 10,000 cases of malaria were confirmed per every 100,000 people in 2010
• Malaria is a major contributor to Sierra Leone having the 4 th lowest life expectancy and 2nd highest infant mortality in the world (below only Afghanistan)
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Haemozoin• All species of the malaria parasite Plasmodium metabolise haemoglobin and excrete the toxic iron molecules as an inert crystal
• These crystals, known as haemozoin, are both magnetic and dichroic, meaning they absorb different polarisations of light in different amounts
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Haemozoin
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Exeter TeamA team of physicists and engineers at the University of Exeter came together to produce a device that could detect haemozoin in the blood
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Haemozoin Biosensor• Aka. MOT (Magneto-Optic Test)
• The MOT detects the presence of haemozoin crystals by applying a magnetic field to a sample of infected blood, aligning them all in the same plane and then shining a polarised light across them
• A sensor at the other end detects changes in light absorption
• The diagnosis of malaria is made on the presumption that the haemozoin it detects is as a result of active infection
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Original MOTThe first MOT device developed
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Current PrototypeThe handheld, portable MOT
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What diagnostics are available?
Rapid Diagnostic Tests (RDTs)
• Cheap and easy to use
• Sensitivity/specificity varies according to brand
• Must be stored in cool, dry environment
• Non-reusable
Microscopy
• Gold standard
• Can differentiate species and give detail on gametocytes, parasitaemia etc.
• Expensive (labor time)
• Requires high level of training + equipment
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Rapid Diagnostic Tests (RDTs)
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Why test for haemozoin?• Present in the blood only during active infection, unlike
antibodies
• Requires just a pinprick of blood
• Quicker: takes just 30 seconds
• Cheaper: initial cost of machine only
• Easier: requires no expert training, gives a simple yes/no diagnosis of malaria
• No special storage requirements
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Objectives• Test 300 patients with ?malaria on the MOT
• To compare these results against both microscopy, two brands of RDT, and in cases of discrepancy, PCR
• Derive sensitivity and specificity values from the data
• As a side project, evaluate the difference in sensitivity and specificity of the two RDT brands in order to identify possible weaknesses in pre-existing rapid diagnostics
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Our lab…
Biosensors
Power supply
Sample prep
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PCR prep
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Results• MOT data under non-disclosure agreement… Data
currently being analysed and will be published in 2012/13
• RDT comparison study showed significant differences between the two brands, with some sacrificing specificity for higher sensitivity and vice versa
• Hospital ran out of their own RDTs mid-way through trial, highlighting the impracticality of disposable tests in poor, rural settings
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As an elective…
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Any questions?